1. Technical Field of Invention
The present invention relates, generally, to power regulation systems and, in particular, to providing precisely regulated power to a microelectronic device such as a microprocessor. Improved power regulation is accomplished with an Active Transient Response Circuit that detects multiple threshold levels and provides multiple levels of gain.
2. Background of the Invention
Regulated power supplies or voltage regulators are typically required to provide the voltage and current supply to microelectronic devices. The regulator is designed to deliver power from a primary source to an electrical load at the specified current, voltage, and power efficiency. Switching power converters (SPC) also referred to as Buck regulators are commonly used voltage regulators due to their high efficiency, high current capability, and topology flexibility. In addition, they can be designed to provide very precise voltage and current characteristics required by devices such as microprocessors, microcontrollers, memory devices, and the like.
Power requirements for emerging leading edge technology microprocessors have become very difficult to satisfy. As the speed and integration of microprocessors increases, the demands on the power regulation system increase. In particular, as gate counts increase, the power regulation current demand increases, the operating voltage decreases and transient events (e.g. relatively large voltage spikes or droops at the load) typically increase in both magnitude and frequency. Some emerging microprocessors are expected to run on less than 1.3 volts and more than 100 amperes.
SPC's utilizing step-down multi-phase Buck converters have been the preferred topology to meet the low voltage and high current requirements of microprocessors. With the advent of increasingly complex power regulation topologies, digital techniques for power converter control, specifically in multiphase designs, can improve precision and reduce the system's total parts count while also supporting multiple applications in the same power system through digitally programmable feedback control.
Existing feedback controls have taken voltage measurements from the load, as well as from the individual output phases. The feedback information has been used to adjust the duty cycle, i.e. width of the pulses produced by each of the phases of a multi-phase buck regulator system to bring the supplied voltage and current within the load line tolerances specified by the microprocessor manufacturer. Such a multi-phase pulse width modulated (PWM) voltage regulator system has been disclosed in the patent applications cross-referenced hereinabove and the details of those disclosures are incorporated herein by reference. In particular, the co-pending patent application entitled: DIGITAL CALIBRATION WITH LOSSLESS SENSING IN A MULTIPHASE SWITCHED POWER CONVERTER, Ser. No. 10/884,840, filed Jul. 2, 2004, inventors: Southwell et al, of which an inventor of this application is a co-inventor, teaches a novel lossless technique for sensing current at the load that is provided in a feedback loop to bring the supplied voltage and current within the specified load line tolerances.
Active Transient Response (ATR) has been used for high frequency response to rapidly changing power requirements at the load by quickly activating multiple phases to supply or drain (as the case required) more current to or from the load, thereby temporarily over riding the generally slower overall voltage regulator system response. Such power regulation systems utilizing ATR have been disclosed in detail in the patent applications cross-referenced hereinabove and the details of those disclosures are incorporated herein by reference. In particular, the co-pending patent application entitled: SYSTEM, DEVICE AND METHOD FOR PROVIDING VOLTAGE REGULATION TO A MICROELECTRONIC DEVICE, Ser. No. 10/103,980, filed Mar. 22, 2002, inventors: Duffy et al, of which an inventor of this application is a co-inventor, discloses a power regulation system having an active transient response (ATR) circuit.
The use of ATR enables voltage regulator systems to be designed with lower overall output capacitance while maintaining equivalent dynamic performance. An ATR circuit includes a window comparator that compares the output supply voltage at the load to the reference voltage, as determined by the specified load line. As long as the output voltage remains within a specified tolerance range (i.e. window) above or below the specified load line, the ATR circuit provides no input signal to the PWM, which proceeds to provide power to the load in a conventional manner. On the other hand, as soon as the voltage is outside the “window”, the ATR circuit signals the PWM to modify its operation. For example, if the voltage drops below the specified voltage range, all low side power switches in the multi-phase system are turned off and then, after a short delay, all high side power switches are turned on, causing the normally staggered inductor charging to occur in parallel.
Thus, when the voltage at the load increases above a specified voltage, the window comparator signals an ATRL (Active Transient Response Low) event. Such an ATRL event requires a rapid lowering of the voltage at the load. This is accomplished by turning on additional low side FETs and blocking the high side from providing the normal synchronous phase pulses. This effectively is a compensation operation that reduces the output voltage. Conversely, when the voltage at the load decreases above a specified voltage, the window comparator signals an ATRH (Active Transient Response High) event. Such an ATRH event causes the high side FETs to increase their duty cycle. This effectively is a compensation operation that increases the output voltage back to within the specified window. This technique of compensating for transients causing over voltage and under voltage conditions is enhanced by adjusting the window comparator to a specified load line. By using AVP (Adaptive Voltage Positioning) as a reference “target voltage”, correction of under voltage and over voltage excursions is improved.
However, as the power regulation needs of load devices such as microprocessors and the like become even more demanding, even more precise ATR techniques than those disclosed in the aforementioned Duffy et al application, are desired. In particular, it is desired to more precisely detect and compensate the magnitude of the voltage excursion from the target voltage.